JPH0637031B2 - Creep feed grinder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a creep feed grinder such as a surface grinder, a cylindrical grinder, and an inner surface grinder.

2. Description of the Related Art In recent years, in the case of this type of grinding machine, the depth of cut into the work is made extremely large compared to normal grinding, and instead the relative speed between the grindstone and the work is made extremely slow, There is a type that employs a so-called creep feed grinding method that improves the grinding efficiency.

In such a creep feed grinding method, as the grinding progresses, the abrasion and wear of the grindstone becomes faster. That is, when the sharpness of the grindstone becomes poor, or when the grinding feed speed is too fast and the grinding feed amount is too large, grinding burn occurs on the grinding object (workpiece) and the work piece often becomes defective.

Therefore, there is also one that adopts the creep feed grinding method in which the grinding wheel is continuously dressed.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a continuous dressing method, the dresser dresses the grindstone even when not grinding, and the grindstone wears very quickly and is wasteful.
Further, the number of times of exchanging the grindstone increases, and it takes a considerable time for the exchanging.

Means for solving the problem Grinding resistance for detecting a grinding burn precursor which is provided with a detecting means for detecting the grinding resistance of the grindstone shaft and returns to a steady value during the grinding A value determining means is provided, and a speed calculating means is provided for setting a grinding feed speed for reducing the grinding resistance value for each preset level after detecting the grinding burn precursor.

Action The sharpness of the grindstone can be known by detecting the grinding resistance of the grindstone shaft by the detecting means. When observing the grinding resistance detected by the detecting means, a peculiar change such as a sharp change in the grinding resistance is shown as a precursor of the case where grinding burn occurs. Therefore, the grinding burn precursor is detected by monitoring the detected grinding resistance and finding the sharp resistance value change by the grinding resistance value determination means. When such a sign of grinding burn is found, the speed calculation means reduces the grinding feed speed so as to reduce the grinding resistance, so that even if grinding burn occurs, the grinding operation can be performed immediately without the occurrence of grinding burn. Continued.

Embodiment An embodiment of the present invention will be described with reference to the drawings. First, an example of a grinder structure will be described with reference to FIG. This grinder 1
Is a saddle 2 that is driven in the front-rear direction, a table 3 that is driven in the left-right direction, a vertical column 4, and this column 4
And a grindstone head 5 held so as to be movable up and down. A work 7 is fixed to the magnet chuck 6 on the table 3. Also, the grindstone head has a grindstone 8
, A whetstone rotating motor 9 directly connected to each other, a dresser rotating motor 11 for driving the dresser 10, and a dresser elevating motor 1 for elevating and lowering a support member holding the motor 11.
2 and 2 are held. Further, on the upper part of the column 4, a grindstone head lifting motor 13 for moving the grindstone head 5 up and down.
Is held.

In the present embodiment, first, the grindstone shaft 8 of the grindstone 8 is first described.
An electric power detector 14 is provided as a detecting means for detecting the grinding resistance R of a. As shown in FIG. 3, the power detector 14 includes a grindstone shaft 8a, and accordingly, a grindstone rotating motor 9
Is connected to. Reference numeral 15 is an input power source.
The power consumption output from the power detector 14 and the grinding resistance to be detected have a linear relationship.
The feed back signal from is captured as a voltage input proportional to the grinding resistance. Therefore, the grinding resistance is R
[Kg / cm ² ], the output voltage from the power detector 14 is E
[V] and power consumption P [KW], E = K ₁ ·
With P and P = K ₂ · R, E = K ₁ · K ₂ · R = K ₃ · R (1) (where K ₁ , K ₂ , and K ₃ are proportional constants) Become.

At this time, the grinding resistance R and the grinding time t have a relationship as shown in FIG. 4 (a) or FIG. 4 (b). Here, FIG. 4 (a) shows the case where the grinding resistance R is changed in three stages of R ₁ , R ₂ and R ₃ (R ₁ > R ₂ > R ₃₎ , and the respective resistance difference is ΔR. Yes). Further, FIG. 4 (b) the grinding resistance R ₁ 'represents a greater than ΔR respect R _2. Here, when the grinding resistance R is observed in detail, if the sharpness of the grindstone 8 becomes poor, or if the grinding feed rate is too fast and the grinding feed amount is too large, the workpiece 7 will eventually be burnt. In such a case, as its precursor, as shown in both FIGS. 4 (a) and 4 (b), it exhibits a peculiar characteristic in which the resistance value sharply changes from a steady value during grinding, and It is understood that the number of times increases as the grinding resistance value increases. This steep change portion M is a precursor of grinding burn.

Therefore, according to such a unique change characteristic of the grinding resistance value, by setting a set value of a certain width (level) with respect to the steady reference value and detecting the deviation of the grinding resistance R from the reference value, The steep change portion M can be easily detected, and this detection time can be grasped as a sign that grinding burn will occur. The grinding feed rate (table feed rate) is controlled based on the detection of the sign of grinding burn, and this control method will be described first.

First, the grinding feed speed v takes an initial setting speed v ₀ when the grinding resistance R is R≈0, and when R = Rmax (the rotary motor 9 for the grindstone).
Of 80% to 95% of the rated value of 1) is set as v = 0. That is, as shown in FIG. 5, in the coordinates showing only the relationship between the grinding resistance value and the grinding speed, (0,
Considering a straight line passing through two points of (v ₀ ) and (Rmax, 0), the grinding feed speed v is represented by v = v ₀ −a · R …………………… (2). Here, the parameter gradient a can be expressed as a function of a = f (n). Where n is the fourth
As shown in FIG. 5A and FIG. 5, it is the number of times (n = 0, 1, 2, ...) That the steep change portion M, that is, the sign of grinding burn is detected at the timing of t ₁ , t _2, etc., The value of the gradient a of the grinding feed speed is changed each time, and control is performed so that actual grinding burn does not occur.

Here, if the gradient a is considered as a linear function of the number of times n, and is set as, for example, a = Kn + b (4) (where K and b are constants), the sign of grinding burn When n = 0 which has not been detected yet, b = v ₀ / Rmax due to a = v ₀ / Rmax. Becomes Therefore, the grinding feed rate v at this time is Becomes

Then, as shown in FIGS. 4 (a) and 5, for example, during grinding (during operation on the characteristic line in these figures) at a grinding resistance of R ₁ and a grinding feed rate of v ₁ . If the sign of grinding burn is captured after the time t ₁ from the start point t ₀ (shown by a) (the first change portion M on the characteristic line, and the change amount is A), the installation value (reference value) as a reference for the detection is obtained. level)
Let B be the value of B, and the value of the gradient a is changed so that the grinding feed rate v is decreased by v ₁ −v ₂ = Δv so that the grinding resistance value becomes R ₁ or R ₂ decreased by ΔR. Speed is Indicated as. As a result, in the grinding operation, the grinding resistance is R
_{At 2} , the grinding feed speed is changed to the grinding operation on the characteristic line by v ₂ . Then, during such a grinding operation, if the grinding burn precursor is detected again at the timing t ₂ (shown by a dot C), the grinding feed rate is reduced so that the grinding resistance is reduced from R ₂ to R ₃ by ΔR. The value of the gradient a is changed so as to decrease by v ₂ −v ₃ = Δv. That is, And As a result, the grinding resistance is changed to R ₃ and the grinding feed rate is changed to v ₃ on the characteristic line.

That is, the point A on the line moves to the line, and the point B on the line moves to the point C on the line. Considering the relationship between the grinding feed rate and time, the control is performed as shown in FIG. 5, and the relationship between the grinding resistance and the grinding feed rate is the sixth.
It is controlled as shown in the figure.

That is, in the present embodiment, the relational expression between the grinding resistance R and the grinding feed speed v is set as shown by the expression (6), and the reference comparison level is a level slightly lower than the grinding resistance at which grinding burn actually occurs. B is set (the level B differs depending on the grinding conditions such as the material of the work 7 and the material of the grindstone 8), and this level B is compared with the grinding resistance detected by the power detector 14. If there is a sharp resistance change A that exceeds, the value of the gradient a that regulates the grinding feed speed is changed according to the equation (5) every time the grinding burn precursor is detected so that the grinding burn does not occur. There is something to do. By controlling the grinding feed speed in this manner, it is possible to continue the grinding operation and perform the grinding process without actually causing the grinding burn. In addition, the adaptive control is performed in the form of the grinding resistance R of the grindstone shaft 8a, which is a comprehensive view of the capacity and grinding conditions of the grinding machine, for example, the state and type of the resistance 8, the material of the work 7, the grinding amount. Is.

By the way, as a grinding machine, in order to improve the grinding efficiency, it is necessary to increase the grinding feed rate as much as possible, but even in the case where the grinding feed rate is gradually reduced as in the present embodiment, This can be dealt with by setting the initial setting speed v ₀ to be slightly higher. That is, when a precursor of grinding burn is detected, a speed close to the maximum that matches the machine capability and grinding conditions is set by itself within a range where grinding burn does not occur, so that grinding efficiency is improved.

Further, unlike conventional methods, continuous dressing, that is, dressing even during non-grinding, reduces unnecessary wear of the grindstone 8 and reduces the number of grindstone replacements.

Therefore, in order to implement such a grinding resistance adaptive speed control system, in this embodiment, for example, a block diagram configuration as shown in FIG. 1 is adopted. First, the output voltage from the power detector 14 is input to the low-pass filter 16 and the band-pass filter 17. Here, low pass filter 16
Is for detecting the DC component R of the grinding resistance.
Further, the band pass filter 17 detects a steep resistance change amount A which is a precursor of grinding burn. If grinding burn occurs during grinding, the amount of change is large, and since there is a certain frequency / amplitude component, it can be detected by the bandpass filter 17. On the other hand, the detection output of the bandpass filter 17 is input to a comparator 18 as a grinding resistance value determining means. The comparator 18 sets the comparison reference level B by the reference setting device 19 slightly lower than the grinding burn generation level A so that the grinding burn does not actually occur. When there is a sharp change in the resistance value that exceeds the change amount A, the comparator 18 outputs a grinding burn precursor detection signal. On the other hand, the output from the band pass filter 17 is also input to the peak hold circuit 20, and the peak value of the steep change amount A that first exceeds the comparison reference level B is held by this peak hold circuit 20. Then, it is converted into a digital signal by the A / D converter 21. Here, the A / D conversion pulse signal of the A / D converter 21 is created by the A / D conversion pulse circuit 22 connected to the output side of the comparator 18. Immediately, one pulse is created when the comparator 18 first operates.

The latch circuit 23 latches the data digitized by the A / D converter 21, and the D / A converter 24 extracts the analog value of the steep change amount a detected first. The output side of the D / A converter 24 is connected to a voltage dividing circuit 25 composed of a resistor and a variable resistor, whereby a constant K = A / m is obtained. here,
m is a constant, and a value of about 2 to 6 is suitable, and the larger the value of m, the smaller the gradient a can be switched. On the other hand, the counter 26 detects the output signal of the grinding burn precursor detection circuit n and thus the comparator 18. These low pass filter 16, counter 26 and D / A converter 2
The output of No. 4 and the initial setting speed v ₀ are input to the speed calculating means 27 side. The speed calculation means 27 is composed of an automatic gain switching amplification circuit 28, an adder 29, a multiplier 30, and a subtractor 31. First, the counter 26
Output, the gain of the automatic gain switching amplifier circuit 28 is switched to obtain the value of Kn. Then, the initial set speed v ₀
Is a resistor and a variable resistor through a voltage dividing circuit 32 to v ₀ / Rm
The adder 29 provided as ax performs addition with the output K · n from the amplifier 28. As a result, the calculation process of (5) is performed. Next, the actual grinding resistance value R (DC component) obtained by the low-pass filter 16 is added by the adder 29.
By being input to the multiplier 30 together with the output from The following arithmetic processing is performed. Next, the calculation result and the initial set speed v ₀ are input to the subtractor 31 and the subtraction process of the equation (5) is performed. Then, this calculation result is output as a command signal of the actual grinding feed speed v through the buffer amplifier 33 to control the speed. Reference numeral 34 is a reset circuit for the A / D converter 21, the A / D conversion pulse circuit 22 and the counter 26.

Effect of the Invention The present invention focuses on the point that when the grinding burn occurs as described above, the grinding resistance shows a sharp change as a precursor thereof,
The sign of grinding burn is found by detecting the grinding resistance of the grindstone shaft and monitoring the detection result, and when a sign is found, the grinding feed rate and the grinding feed rate that decrease the grinding resistance value for each preset level Since it is controlled so that grinding can be performed in a state where there is very little grinding burn, the grinding can be efficiently continued at the optimum grinding feed speed suitable for that time, and the continuous dressing method As it is not like dressing even when not grinding,
It is also possible to prevent unnecessary wear of the grindstone.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a block diagram, FIG. 2 is a side view of a grinder, FIG. 3 is a front view showing a part of the grinding machine, and FIG. FIG. 5 is a characteristic diagram showing the relationship between grinding resistance, FIG. 5 is a characteristic diagram showing the relationship between time and grinding feed rate, and FIG. 6 is a characteristic diagram showing the relationship between grinding resistance and grinding feed rate. 8 ... Whetstone, 8a ... Whetstone shaft, 14 ... Power detector (detection means), 18 ... Comparator (grinding resistance value determination means), 27 ... Speed calculation means

Claims (1)

[Claims] 1. A detection means for detecting a grinding resistance of a grindstone shaft,
Grinding resistance value determining means for detecting a grinding burn precursor that returns to a steady value during grinding during the grinding based on the detecting means, and a grinding resistance value for each preset level after detecting the grinding burn precursor. And a speed calculation means for setting a grinding feed speed to be reduced to 1.